Bootstrap MaxLength plugin integrates by default with Twitter Bootstrap using badges to display the maximum lenght of the field where the user is inserting text. This plugin uses the HTML5 attribute "maxlength" to work.
The indicator badge show up on focusing on the element, and disappear when the focus is lost.
NobleCount is a customizable jQuery plugin for a more improved counting of the remaining characters, and handling of resulting behaviors, of a text entry object, e.g. input textfield, textarea. Also, NobleCount supports pre-existing text within the text object and jQuery chaining.